Difference between revisions of "Category:Pericardial Pathology"

The heart is invested in a pericardial sac with both visceral and parietal components. The visceral layer is closely adherent to the heart wall. The space within the pericardium is small and contains approximately 1-5ml serous fluid. This allows smooth movement of the heart within the pericardium during normal systole and diastole.
The pericardial sac is thin, fibrous and inelastic so prevents and significant distension. This causes a constrictive effect when fluid accumulates within the sac.

Pericardial disease accounts for only 1% of all clinically significant cardiac disease in the dog and cat, however it a frequently overlooked cause of right heart failure. Pericardial disease which is clinically significant is rare in the cat.

The most common congenital abnormality of the pericardium is Peritoneo-pericardial diaphragmatic hernia.

Other congenital abnormalities of the pericardial sac include:

• Pericardial cysts.
• Partial or complete absence of the paricardial sac.

Metabolic Pathology

Serous atrophy of fat

Epicardial mineralisation

Urate deposition

Hydropericardium

Haemopericardium

Haemorrhagic effusion

Fluid accumulation within the pericardial sac may lead to fibrous thickening and opacity of the pericardium if prolonged. Villous proliferation of the serosa will occur due to the irritation caused by the presence of the fluid.

Large volumes of fluid within the pericardial sac may cause cardiac tamponade.

Idiopathic in giant breeds of dog E.g. St Bernard.

Inflammatory-Pericarditis

Usually an infective aetiology. As with non-inflammatory accumulation of fluid the main complication is the restriction of ventricular movement. Clinical signs seen are therefore those of circulatory failure along with pyrexia and a general depression.

Pericarditis. Courtesy of A. Jefferies

Spread of infectious agent may be:

• Haematogenous; following generalised infection. Most often seen in cattle and pigs.
• Extension of infection form surrounding tissues; for example from the lungs, pleura, mediastinum.
• Extension of infection from myocardium; rare.
• Traumatic penetration of the pericardium;
  • Foreign bodies from the oesophagus or reticulum in cattle; traumatic reticulo-peritonitis.
  • Fractured ribs; E.g. RTAs in small animals, horses etc.

Pericarditis can be subdivided into two main categories:

Fibrinous pericarditis

Fibrinous pericarditis. Courtesy of A. Jefferies

Most common form. Grey strands of fibrin cover the epicardium and little fluid accumulates. Close apposition of the parietal and visceral pericardium layers allows adhesion formation within approximatley 7-10 days. Such adhesions may resolve with little residual pathology or may become focal or diffuse adhesive pericarditis lesions.

Fibrinous pericarditis produces a crackiling sound on auscultation.

Suppurative pericarditis

Traumatic pericarditis. Courtesy of A. Jefferies

Purulent pericarditis indicates the presence of pyogenic organisms E.g. Staphs Usually occurs in cattle as a result of traumatic penetration of the pericardial sac with a sharp metallic object or wire. This is Traumatic reticulo-peritonitis Death usually occurs before organisation and a constrictive pericarditis can become apparent.

Traumatic pericarditis. Courtesy of A. Jefferies

Traumatic pericarditis. Courtesy of A. Jefferies

Sequalae of pericarditis:

• Resolution with no further clinical significance.
• Adhesion: organisation of fibrin. May lead to a bread and butter appearance.
• Constriction: gradual cardiac tamponade will occur.